linux-kernel - Re: [PATCH] host1x: cdma: use completion instead of semaphore

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Message-ID: <CAK8P3a08VEReXUZ39f3iQS3wUZSwKYObnn-jQrUiMJ4Gyx6hVQ@mail.gmail.com>
Date:   Tue, 11 Dec 2018 11:11:38 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Mikko Perttunen <cyndis@...si.fi>,
        Dmitry Osipenko <digetx@...il.com>, emil.fsw@...de.io,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] host1x: cdma: use completion instead of semaphore

On Tue, Dec 11, 2018 at 11:08 AM Thierry Reding
<thierry.reding@...il.com> wrote:
>
> On Mon, Dec 10, 2018 at 10:51:04PM +0100, Arnd Bergmann wrote:
> > In this usage, the two are completely equivalent, but the
> > completion documents better what is going on, and we generally
> > try to avoid semaphores these days.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  drivers/gpu/host1x/cdma.c | 6 +++---
> >  drivers/gpu/host1x/cdma.h | 4 ++--
> >  2 files changed, 5 insertions(+), 5 deletions(-)
>
> My understanding is that potentially many userspace processes could be
> blocking on this, which I think is the reason for it being a semaphore.
> Is the completion going to work for those cases as well?

Yes, it behaves the exact same way here.

       Arnd